Typical trunked communication systems have a limited number of communication resources which are efficiently allocated among a plurality of communication units by at least one communication resource controller. Any of the plurality of communication units may gain access to one of the communication resources by transmitting an inbound signalling word (ISW) to the communication resource controller. The ISW generally contains the communication unit's individual identification code, the communication unit's group affiliation, if it has one, and an op-code requesting access to one of the communication resources. After verfying the ISW, the communication resource controller allocates one of the communication resources to the communication unit which sent the ISW, if the ISW is valid and a communication resource is available.
Once a communication unit has been granted access to a communication resource, the communication unit, or units, intended to receive the call, are notified of the communication resource to be used and the individual identification code of the transmitting communication unit. The receiving communication unit, or units, may be any communication unit having the same group affiliation as the transmitting communication unit, or any communication unit which was specifically identified by the transmitting communication unit.
A receiving communication unit generally displays the transmitting communication unit's individual identification code such that the operator of the receiving communication unit may identify the operator of the transmitting communication unit (caller). The display is usually limited to a particular size and alpha-numeric format. For example, the display may comprise a binary, decimal, or hexadecimal representation of the individual identification code such as 10101010, 146967, or FE43A; respectively, or it may comprise an alpha-numeric alias of the individual identification code such as UNIT 12.
An operator of a receiving communication unit may have a difficult time identifying the caller based on the individual identification code, especially in a large trunked communication system or when the transmitting unit is not part of a fixed dispatch operation. Unless the operator of the receiving communication unit has associated a caller with an individual identification code, it may not be able to identify the caller. This may become a substantial limitation when the identity of the caller must be known. For example, the caller's identity is often required in trunked communication systems where security, call logging, or user-vehicle association is a primary concern.
Therefore, a need exists for a method and apparatus in which an operator of a receiving communication unit may easily identify the operator of a transmitting communication unit.